Heretofor, electrical discharge machines have typically included a carriage mounted thereon for guided movement in a vertical direction, with either a single electrode or a pair of like or different electrodes removably mounted via suitable quick change means on the carriage. While such arrangements are satisfactory, it is desirable to incorporate means for mounting and indexing into operational position a plurality of single or double electrode cartridge assemblies on one electrical discharge machine, in order to eliminate having to remove and replace electrodes in a particular cartridge assembly each time the electrodes become worn or a different size or pattern is required.